Perspective conformal lateral deviation symbology provides intuitive displays to flight crews of current position in relation to an intended flight path. In particular, lateral deviation symbology indicates to a flight crew the amount by which the aircraft has deviated to the left or right of an intended course. Deviation bars on perspective conformal lateral deviation symbology represent a fixed ground distance from the intended flight path. As the aircraft pitches, ascends or descends, the display distance between the deviation bars will vary. However, the actual ground distance from the intended flight path represented by the deviation bars remains the same. Therefore, flight crews can determine position information with reduced workload by merely observing the position of the aircraft in relation to the deviation bars. Regardless of attitude or altitude, flight crews know how far off course an aircraft is if the aircraft is a given number of deviation bars from the intended flight path.
In order to maintain the conformal view, the lateral deviation symbology moves on the display in relation to movement of the intended flight path's display position. However, due to that movement, the symbology can temporarily disappear from the display at certain attitude and heading orientations. For example, if the aircraft is too far off course, the symbology may move too far to the left or right and, consequently, move off the display. Likewise, if the aircraft is at too great a pitch angle, the symbology may move off the top or bottom of the display. Flight crews, therefore, do not have a continuous display of lateral deviation information. An additional problem is that the symbology may move and overlap other primary flight information such as altitude or ground speed tapes. This overlapping makes it more difficult to view the primary flight information and the lateral deviation symbology.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a dynamic lateral deviation display which enables flight crews to continuously determine lateral deviation information, regardless of attitude or heading, while not interfering with other primary flight information.